A scrambler bike rider who died after his off-road vehicle hit a wall may have been chased shortly before the crash, police said.
Adam Egan, 24, had been critically ill in hospital since the collision in Longmoor Lane, Fazakerley, Liverpool, at about 4.40pm on Tuesday.
The father-of-one from Liverpool died on Saturday.
On Monday, Det Insp Paul Speight, of Merseyside Police, said: "We are investigating the possibility that Mr Egan was being chased shortly before the incident and are very keen to hear from anyone who might have information that could help our inquiries.
"If you noticed anything suspicious, or any vehicles being driven at speed in the area at the time of the incident, please contact police as that information could prove vital.
"Also, if you have any CCTV or dashcam footage taken in the Longmoor Lane area before or after 4.40pm on Tuesday 27 March, that footage could be significant and we would ask you to contact police."
Anyone with information on the collision should contact Matrix Roads Policing on 0151 777 5747, or Merseyside Police social media desk via Twitter @MerPolCC or Facebook Merseyside Police CC. Or call 101 quoting incident reference 18200065123 or contact the independent charity Crimestoppers anonymously on 0800 555 111.